I understand this is not professional advice or anything like that, but I have to make quick decisions on an auction property and BP is a great resource for more insight / other folks take on it.How would you seal something like this up, just bolt a cover over it, or actually fill it in? 

Mike, You would need to figure your costs, if it costs you 150K to add that floor, will the rent cover your loan payments and increased taxes while still giving you a profit ?

This does present a hurdle to RE investors when they are first starting out because most of these new RE investors  do not have much excess cash to cover a large capital expense (or even a moderate cap expense). 

Is normal Airbnb lucrative enough to cover that type of mortgage?  

Kitchen: This category is where I cover all of what I consider kitchen costs.

Using that you can determine if the rents at your potential facility will be high enough to cover the cost of construction and turn a profit. 

There is a lot of things to be covered pertaining to the ups and downs.

The property's risk to flood is rather unique (and has increased in the last few years), but I want to make sure if there is any risk to the tenants, they are covered.

Depending on what it is, $12k may not cover the rehab, so keep that in mind as well.

He simply covers the mortgage for the property.